Here are some pics of my mobile robot prototype built at Hexagram. It uses 2 ultrasonic range finders and an IR sensor to navigate space (control 2 planetary gear motors via 2 MD03 motor controllers via an Arduino + code). I also started an IR homing system (like a remote control); an IR transimitter, receivers and a battery level monitoring circuit. The plan is that when the battery is low No.1 will go to the recharge station or in this case the IR transmitter. It kinda worked but the range of the IR is limited and i need better knowledge of C++ for precise navigation. No.1 is a tuff little critter that can push about wheeled bins and light chairs.
The docking circuit came from this site.